DE102014013433A1 - Sensor control device - Google Patents

Abstract

A gas sensor control device (2) comprises a digital control unit (31) (in particular a CPU 91) which functions as a digital filter unit (99). Even if high-frequency noise components are superposed on an electrical signal transmitted from the electromotive force cell (24) to the digital control unit (31), the high-frequency noise components can be canceled by the digital filter unit (99). Thus, a terminal voltage across both terminals of the electromotive force cell (24) corresponding to the oxygen concentration can be suitably extracted. The digital control unit 31 can appropriately feedback-control the pumping current Ip based on the terminal voltage Vs generated across both terminals of the electromotive force cell (24) while suppressing the influence of high-frequency noise components.

Description

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a sensor control apparatus for controlling a sensor comprising a diffusion chamber, an electromotive force cell, and a pumping cell.

2. Description of the Related Art

Known sensors for linearly detecting oxygen over a wide concentration range in an exhaust gas discharged from an internal combustion engine include a diffusion chamber into which a gas to be measured (exhaust gas) flows through a diffusion rate controlling layer, and two cells, that is, an electromotive type Kraft cell (oxygen concentration measuring cell), which is equipped with electrodes on a solid electrolyte layer, and a pump cell (oxygen pump cell).

In order to maintain a detection voltage (voltage Vs) output from the electromotive force cell of this sensor at a predetermined value (target voltage value), there is provided a sensor control device configured to supply a pumping current supplied to the pumping cell to control feedback, thereby controlling the sensor.

Nevertheless, a case may occur in which the feedback control can not be adequately performed due to factors such as variations in a characteristic of the sensor or the environment of use, and whereupon the pumping current value becomes unusable. Therefore, the detection voltage of the electromotive force cell does not converge to the target voltage value, thereby causing oscillations in the feedback control performed by the sensor control device.

To address this problem, there is a known technique in which, for example, the inner side electrode of a pump cell and the detection electrode of an electromotive force cell are formed as a common electrode, and a leakage resistance having a small resistance is added to the common electrode (see Japanese Patent No. 2624704 ). Further, there is another known technique in which a feedback resistor is added in parallel to the outside electrode of a pumping cell and the cell electrode of an electromotive force cell, and a voltage having the same phase as that of the pumping current is superimposed on a voltage Vs thereby suppressing oscillations (see JP-A-5-256817 ).

Further, still another technique has been proposed in which a high frequency component of a pumping current obtained by canceling low frequency components of a predetermined cutoff frequency or lower frequencies from a pumping current is caused to flow to an electromotive force cell to thereby cause oscillations of one a control circuit connected to a sensor (see JP-A-2002-243700 ).

3. Problems to be solved by the invention

However, by causing high-frequency components of the pumping current to flow to the electromotive force cell, according to the abrupt change of the pumping current, an immediately large current (current spike) flows into the electromotive force cell, whereby the electromotive force cell may be damaged.

For example, shortly after the pumping current begins to flow, the pumping current may be e.g. B. shortly after the activation of the sensor, change abruptly. In such a case, since an abrupt change in the pumping current is caused by the high-frequency components, the high-frequency components flow into the electromotive force cell. Consequently, a current spike flows into the electromotive force cell, whereby the electromotive force cell can be damaged.

Therefore, it is an object of the invention to provide a sensor control apparatus which, while feedback-controlled pumping current based on a detection voltage, can suppress oscillations of the detection voltage without using a configuration causing high-frequency components of the pump current to become electromotive Force cell flow.

SUMMARY OF THE INVENTION

The above object has been achieved by providing (1) a sensor control apparatus for controlling a sensor, the sensor comprising a diffusion chamber into which a gas to be measured flows through a diffusion rate controlling layer, an electromotive force cell having a detection voltage corresponding to a concentration of generated a particular gas component within the diffusion chamber, and a pump cell, which pumps the specific gas component according to an externally provided pumping current in or out of the diffusion chamber, wherein the sensor control device comprises: a control unit which is configured to the pumping current fed back feedback controlled based on the detection voltage so that the detection voltage generated at the electromotive force cell approaches a target voltage; and a low-pass filter unit configured to extract a predetermined low-frequency component from the detection voltage, wherein the control unit feedback controls the pumping current based on the low-frequency component extracted by the low-pass filter unit.

The detection voltage generated in the electromotive force cell in accordance with the concentration of the particular gas component is modified by the low-pass filter unit to generate a low-frequency electrical signal that is proportional to the voltage generated by the pumping current at both terminals of the pumping cell Time unit changed by a small amount.

Therefore, even if high frequency noise components, e.g. B. the voltage generated across both terminals of the pump cell, the detection voltage are superimposed, the detection voltage and the high-frequency noise components are separated by the difference of their frequency bands is used. That is, the low-frequency components extracted from the detection voltage by the low-pass filter unit are free of high-frequency noise components and thus equivalent to an "actual detection voltage" corresponding to the concentration of the specific gas component in the electromotive force cell becomes.

Accordingly, when the control unit feedback controls the pumping current based on the low-frequency components extracted by the low-pass filter unit, the pumping current can be feedback-controlled based on an "actual detection voltage" while suppressing the influence of the high-frequency noise components.

Therefore, the invention can avoid control of the pumping current fed back to an unusable value, and the control unit can control the detection voltage to approach the target voltage and suppress oscillations of the detection voltage.

In other words, according to the invention, the detection voltage can be made to approach the target voltage by feedback controlling the pumping current based on the low-frequency components extracted by the low-pass filter unit. This is done without using a configuration in which pumping current with high frequency components flows to the electromotive force cell. This is achieved by canceling the low frequency components of a predetermined cutoff frequency or frequencies below from the pumping current.

Thus, according to the invention, during the detection voltage based feedback control of the pumping current, oscillations of the detection voltage can be suppressed without using the configuration in which the high frequency components of the pumping current flow to the electromotive force. In particular, as the predetermined low-frequency components set in the low-pass filter unit, low-frequency components can be set in a range in which the sensor normally acts with respect to the configuration, etc., of the sensor. For example, the low-frequency components extracted by the low-pass filter unit may be set such that the phase of the frequency characteristic of the control transfer function of the sensor and the sensor control device does not reach -180 degrees in a frequency range in which a gain 0 dB or more to suppress oscillations.

According to a preferred embodiment (2), the sensor control device (1) further comprises an analog-to-digital voltage converter which converts the detection voltage generated at the electromotive force cell of the sensor from an analog value to a digital value, wherein the low-pass filter unit is a digital Performs operation on the digital value of the detection voltage converted by the analog-to-digital voltage converter to thereby extract the low-frequency component, and wherein the control unit feedback-controls the pumping current through a digital process based on the digital value of the low-frequency component.

In this way, a configuration is provided in which the analog-to-digital voltage converter converts the detection voltage from an analog value to a digital value and the low-pass filter unit extracts the low-frequency components by a digital operation. As a result, the low-frequency components can be extracted from the detection voltage.

According to a further preferred embodiment (3), the sensor control device (1) further comprises a low-frequency analog / digital converter which converts the low-frequency component extracted by the low-pass filter unit from an analog value into a digital value, the low-pass filter Unit is an analog circuit which is in a detection path of Detection voltage from the electromotive force cell is provided to the control unit, and wherein the control unit, the pumping current by a digital process, based on the digital value of the converted from the low-frequency analog / digital converter, low-frequency component, fed back.

In this way, the low-pass filter unit is configured as an analog circuit, and further provided is a low-frequency analog-to-digital converter which converts the low-frequency component extracted by the low-pass filter unit from an analog value to a digital value. Thus, the low-frequency component can be extracted from the detection voltage.

Effects of the invention

The invention may perform a feedback control of the pumping current based on a detection voltage generated by an electromotive force cell in accordance with the concentration of a particular gas component, while the influence of high frequency noise components, e.g. B. the voltage generated across both terminals of the pumping cell, is suppressed. Thus, the detection voltage can be controlled so as to approach the target voltage, and oscillations of the detection voltage can be suppressed.

According to the invention, while the pumping current is feedback controlled based on the detection voltage, oscillations of the detection voltage can be suppressed without using a configuration causing a high-frequency component of the pumping current to flow to the electromotive force cell.

BRIEF DESCRIPTION OF THE DRAWINGS

1 FIG. 15 is a diagram showing the overall configuration of a control system for an internal combustion engine including a gas sensor control device.

2 Fig. 10 is a diagram showing the schematic configuration of a gas sensor.

3 FIG. 10 is a functional block diagram of a process control executed by a processor (CPU) of a digital control unit.

4 FIG. 15 is a diagram showing the overall configuration of a second engine control system including a second gas sensor control device.

5 Fig. 10 is a functional block diagram of a process control executed by a processor (CPU) of a digital control unit of the second embodiment.

6 Fig. 10 is a circuit diagram of a low-pass filter of the second embodiment.

7 is a circuit diagram of a second low-pass filter.

8th is a circuit diagram of a third low-pass filter.

Description of the reference numerals

Reference numerals used to indicate various features in the drawings include:

LIST OF REFERENCE NUMBERS

1

Internal combustion engine control system

2

Gas sensor control device

8th

gas sensor

14

pumping cell

18

porous diffusion layer

20

diffusion chamber

24

electromotive force cell

31

digital control unit

91

Processor (CPU)

93

first A / D converter

94

D / A converter

97

second A / D converter

98

Digital signal receiving unit

99

digital filter unit

100

Pump current control unit

101

second internal combustion engine control system

102

second gas sensor control device

111

Low Pass Filter

121

second low-pass filter

131

third low pass filter

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments will be described in detail with reference to the drawings. However, the invention should not be construed as being limited thereto.

1. First embodiment

1.1. overall configuration

1 As an embodiment in which the invention is applied, the overall configuration of a control system 1 for an internal combustion engine including a gas sensor control device 2 includes,

The engine control system 1 performs, for example, an air-fuel ratio control, etc. of the internal combustion engine and is used to control the operating state of the internal combustion engine. The gas sensor control device 2 is used to detect a particular gas component (oxygen in this embodiment) within the exhaust gas of the internal combustion engine.

The engine control system 1 includes at least the gas sensor control device 2 , a gas sensor 8th and an engine control unit 9 ,

The gas sensor control device 2 detects a gas detection signal and an element resistance value signal of the gas sensor 8th , which is arranged in the exhaust pipe of the internal combustion engine (engine), and outputs the gas detection signal and the element resistance value signal to the engine control unit 9 (Motor CPU 9 ) out.

The gas sensor 8th detects linearly over a wide range of oxygen concentration within the exhaust gas. The engine control unit 9 controls the air-fuel ratio of the engine using the gas detection signal as one of the many types of flow control.

The gas sensor control device 2 includes a digital control unit 31 to perform the various types of sequencing, a first operational amplifier 33 , a second operational amplifier 35 , a third operational amplifier 37 , Connections 39 for external connections, a constant current output unit 61 , a constant current source circuit 62 , a serial communication port 53 , Etc.

The connections 39 for external connections include ports (a Vs + port 41 , a pout connection 45 , a Vicent connection 47 , a COM port 49 and an Ip + connection 51 ), with the gas sensor 8th connected, and a capacitor connection 43 that with a capacitor 57 connected is.

The constant current output unit 61 gives a constant current for detecting the resistance value of the internal resistance of the gas sensor 8th out. The constant current source circuit 62 gives a constant current (low current Icp) to an electromotive force cell 24 out.

The serial communication port 53 transmits / receives various kinds of signals (gas detection signal, element resistance value signal, etc.) to / from the engine control unit 9 via a cable for serial communication 85 ,

The schematic configuration of the gas sensor 8th is in 2 and a brief explanation of the gas sensor is given below.

The gas sensor 8th includes a pumping cell 14 , a porous diffusion layer 18 , the electromotive force cell 24 and a reinforcing plate 30 ,

The pump cell 14 comprises an oxygen ion-conducting solid electrolyte 13 composed of partially stabilized zirconia (ZrO ₂ ) and porous electrodes 12 . 16 consisting mainly of platinum on front and back surfaces of the solid electrolyte 13 are formed. The electromotive force cell 24 comprises an oxygen ion-conducting solid electrolyte 23 composed of partially stabilized zirconia (ZrO ₂ ) and porous electrodes 22 . 28 consisting mainly of platinum on front and back surfaces of the solid electrolyte 23 are formed.

The porous electrode 16 the pump cell 14 that is a diffusion chamber 20 facing, and the porous electrode 22 the electromotive force cell 24 that of the diffusion chamber 20 are facing each other, are electrically connected to each other and are in turn connected to the sensor COM port 17 of the gas sensor 8th connected. The sensor COM port 17 of the gas sensor 8th is with the Vicent connection 47 and the COM port 49 the gas sensor control device 2 connected and also with the Pout connection 45 via a current detection resistor 83 connected (see 1 ).

The porous electrode 12 the pump cell 14 is with the sensor Ip + connector 19 of the gas sensor 8th connected while the porous electrode 28 the electromotive force cell 24 with the sensor Vs + connector 15 of the gas sensor 8th connected is. The sensor Ip + connector 19 is with the ip + connection 51 the connections 39 connected to external connections while the sensor Vs + terminal 15 with the Vs + connection 41 the connections 39 connected to external connections (see 1 ).

The reinforcement plate 30 is over a layer forming the reference chamber 29 on the electromotive force cell 24 glued, leaving a reference oxygen chamber 26 between the reinforcing plate and the electromotive force cell 24 is formed. The porous electrode 28 the electromotive force cell 24 is located at the reference oxygen chamber 26 at.

The diffusion chamber 20 that of the porous diffusion layer 18 is surrounded, is between the pumping cell 14 and the electromotive force cell 24 educated. In other words, the diffusion chamber communicates 20 with the measurement gas atmosphere over the porous diffusion layer 18 , Although this embodiment is the porous diffusion layer 18 When it is formed by filling an empty space with porous material, it is possible to increase the velocity of the gas to be measured entering the diffusion chamber 20 flows, by setting up small holes instead of the porous diffusion layer.

The gas sensor 8th includes a heater 42 , The pump cell 14 and the electromotive force cell 24 are activated by heating them 42 be heated, whereby a gas detection is possible.

Next, the oxygen concentration measurement operation of the gas sensor control device will be described 2 regarding 1 described.

In the gas sensor control device 2 is a pumping current Ip, which enters the pumping cell 14 flows, so controlled, that a terminal voltage Vs across both terminals of the electrometric force cell 24 is achieved, a target voltage value (450 mV in this embodiment) is achieved, while a constant small current Icp is brought to from the constant current source circuit 62 to the electromotive cell 24 to flow and thereby pump oxygen into and out of the diffusion chamber.

Since the current value and the flow direction of the pumping current Ip, passing through the pumping cell 14 flows, according to the oxygen concentration (air-fuel ratio) of the exhaust gas, the oxygen concentration of the exhaust gas can be calculated based on the value of the pumping current Ip. Thus, when the small current Icp is brought to it, it is in a direction toward the electromotive cell 24 to flow, which is the pumping out of oxygen from the diffusion chamber 20 towards the side of the porous electrode 28 corresponds, the reference oxygen chamber works 26 as an internal oxygen reference source.

At the third operational amplifier 37 is an inverting input terminal to the Vicent terminal 47 A reference voltage (+3.6 V) is applied to the non-inverting input terminal and an output terminal is connected to the sensor Ip + terminal 19 the pump cell 14 connected.

1.2. Digital control unit

The following is the digital control unit 31 described.

The digital control unit is configured by a known microcomputer having a CPU, a ROM, a RAM, etc. The digital control unit 31 according to this embodiment is configured to a central processing unit 91 (hereinafter also as processor or CPU 91 designated), an EEPROM 92 , a first A / D converter (Analog / Digital) 93 , a D / A converter (digital / analog) 94 , an I / O unit 95 (Input / output), a serial transmission / reception unit 96 , a second A / D converter 97 , etc. to include.

The processor (CPU) 91 performs various types of flow control operations. The EEROM 92 is a storage unit that stores the contents of various scheduling operations and a parameter set, etc. The RAM (not shown) is a storage unit that temporarily stores control data, etc.

The A / D converter is a converter that converts an analog signal into a digital signal. The digital control unit 31 includes the first A / D converter 93 to the output voltage of the first operational amplifier 33 to undergo an A / D conversion, and a second A / D converter 97 to the voltage at the Vicent connection 47 to undergo the A / D conversion.

The D / A converter is a converter that converts a digital signal into an analog signal. The digital control unit 31 includes the D / A converter 94 to the resistance 81 To be issued voltage to a D / A conversion.

The I / O unit is an input / output unit to provide a binary signal, e.g. B. an "on" and "off" signal, input and output. The digital control unit 31 includes the I / O unit 95 for outputting a control command signal to the constant current output unit 61 ,

The serial transmission / reception unit 96 is a transmission / reception unit that performs serial communication according to a predetermined transmission protocol. In the digital control unit 31 transmits or receives the serial transmission / reception unit 96 a signal to or from at least the engine control unit 9 by means of a serial communication.

The digital control unit 31 (especially the CPU 91 ) detects a voltage difference between the voltage at the sensor Vs + terminal 15 and the voltage at the Vicent connection 47 (Terminal voltage Vs across both terminals of the electrometric force cell 24 is generated) and controls the magnitude of the pumping current Ip that goes to the pumping cell 14 flows, fed back through PID control so that the electromotive force (terminal voltage Vs) of the electromotive force cell 24 450 mV. In particular, the digital control unit performs 31 a PID control based on the deviation ΔVs between the setpoint voltage (450 mV) and the terminal voltage Vs of the electromotive force cell 24 based, and controls the output voltage of the second operational amplifier 35 such that the deviation ΔVs approaches 0 (in other words, the terminal voltage Vs approaches the target voltage), whereby the pumping current Ip, that of the third operational amplifier 37 to the pumping cell 14 flows, is controlled.

The pumping current Ip flows from the pumping cell 14 to the output terminal of the third operational amplifier 37 or from the output terminal of the third operational amplifier 37 to the pumping cell 14 depending on the polarity, ie, depending on the positive or negative value of the polarity.

The digital control unit 31 (especially the CPU 91 ) performs a multiplication operation between the magnitude of the pump current Ip calculated by the PID control and the resistance value Rd of the current detection resistor 83 to thereby supply the terminal voltage across both terminals of the current detection resistor 83 as the gas detection signal (signal Vip) to detect. Then there is the digital control unit 31 the gas detection signal (signal Vip) via the serial communication port 53 to the engine control unit 9 out.

The engine control unit 9 calculates a corresponding oxygen concentration from a map (the map represents a correlation between the gas detection signal and the oxygen concentration) stored therein based on the gas detection signal (signal Vip). Furthermore, the engine control unit leads 9 performs a detection process of the air-fuel ratio based on the calculated oxygen concentration, and also performs an air-fuel ratio processing such that the air-fuel ratio reaches a target air-fuel ratio.

1.3. Operation to measure the resistance value (temperature) of the electromotive force cell

Hereinafter, an operation for measuring the internal resistance value Rpvs (temperature) of the electromotive force cell 24 the gas sensor control device 2 described.

The constant current output unit 61 the gas sensor control device 2 includes a first switch 63 , a first constant current source circuit 65 , a second switch 67 , a second constant current source circuit 69 , a third switch 71 , a third constant current source circuit 73 , a fourth switch 75 and a fourth constant current source circuit 77 ,

The first switch 63 , the first constant current source circuit 65 , the second switch 67 and the second constant current source circuit 69 are provided to provide an N-pulse constant current (-I const) for detecting Rpvs of the electromotive force cell 24 to flow. The third switch 71 , the third constant current source circuit 73 , the fourth switch 75 and the fourth constant current source circuit 77 are provided to provide a P-pulse constant current (+ I const) for detecting Rpvs to the electromotive force cell 24 with the polarity of the N-pulse constant current for detecting the Rpvs being opposite to the polarity of the P-pulse constant current.

The digital control unit 31 the gas sensor control device 2 is configured to set the digital value of the terminal voltage Vs of the electromotive force cell 24 in the RAM (not shown) of the CPU's flow control 91 to thereby store the terminal voltage Vs of the electromotive force cell 24 to palpate and hold.

That is, during the measurement of the resistance value of the electromotive force cell 24 As a constant current is caused to change from the constant current output unit, it changes 61 to the electromotive force cell 24 to flow, the terminal voltage Vs of the electromotive force cell 24 due to the influence of the constant current. If, in contrast, the digital control unit 31 the terminal voltage Vs of the electromotive force cell 24 samples and stops just before the constant current from the constant current output unit 61 to the electromotive force cell 24 begins to flow, the digital control unit can 31 perform a PID control by using the terminal voltage Vs just before the measurement of the resistance value.

Furthermore, the digital control unit calculates 31 a voltage difference ΔVr (= | Vs1-Vs2 |) between a voltage Vs1 before the measurement and a voltage Vs2 in the measurement of the electromotive force cell 24 , The voltage Vs1 before the measurement is the terminal voltage Vs of the electromotive force cell 24 , sampled and held before the constant current from the constant current output unit 61 begins to flow. The voltage Vs2 in the measurement is the terminal voltage Vs of the electromotive force cell 24 while the N-pulse constant current (-I const) flows to detect the Rpvs. Since the voltage difference ΔVr is proportional to the resistance value of the internal resistance of the electromotive force cell 24 is, this voltage difference can be used as an element resistance value signal SRpvs, which is the resistance value of the internal resistance of the electromotive force cell 24 represents.

This means; the digital control unit 31 is configured by calculating the voltage difference ΔVr, the output of the element resistance value signal SRpvs, which is the value of the internal resistance of the electromotive force cell 24 represents, to enable. In particular, the digital control unit performs 31 an SRpvs measurement procedure in which the element resistance value signal SRpvs is obtained by dividing the voltage difference ΔVr by the current value of the N-pulse constant current (-I const) to detect the Rpvs. The element resistance value signal SRpvs is proportional to the resistance value Rpvs of the internal resistance of the electromotive force cell 24 and is also at the temperature of the electromotive force cell 24 proportional.

A constant period is necessary until the terminal voltage Vs (voltage Vs2 in the measurement) of the electromotive force cell 24 becomes stable after the N-pulse constant current (-I const) starts to flow to detect the Rpvs. Thus, the digital control unit performs 31 the detection process of the terminal voltage Vs (voltage Vs2 in the measurement) of the electromotive force cell 24 after a stand-by period for detecting the Rpv has elapsed since the beginning of the N-pulse constant current (-I const) flow to detect the Rpvs.

The digital control unit 31 (especially the CPU 91 ) outputs the element resistance value signal SRpvs obtained by the Rpvs measurement procedure via the serial communication port 53 to the engine control unit 9 out.

The engine control unit 9 controls the power supply to the heater 42 to the gas sensor 8th to heat, based on the element resistance value signal SRpvs, such that a value corresponding to the resistance value Rpvs of the internal resistance of the electromotive force cell 24 correlates, reaches a setpoint. This temperature control acts to the temperature of the gas sensor 8th at a set point (eg 800 ° C) to keep, so the amount of electricity, that of heating 42 is supplied, as soon as the temperature of the electromotive cell is reduced 24 greater than the set point, whereas the amount of electricity is that of the heating 42 is added, as soon as the temperature of the electromotive cell 24 lower than the setpoint.

1.4. Terminal voltage Vs of the electromotive cell

Now follows a description of the effects that can be achieved by using a low pass filter flow in the CPU 91 the digital control unit 31 is performed while a control is performed to the terminal voltage Vs of the electromotive force cell 24 be controlled so that it approaches the target voltage.

3 is a functional block diagram of a flow control used by the CPU 91 the digital control unit 31 for controlling the pumping current Ip based on the terminal voltage Vs of the electromotive force cell 24 is performed.

As in 3 shown, the processor includes 91 , as functional blocks, a digital signal receiving unit 98 , a digital filter unit 99 and a pumping current control unit 100 ,

The digital signal receiving unit 98 receives a digital signal which is an electrical signal from the electromotive force cell 24 via the Vs + connection 41 to the operational amplifier 33 transmitted and from the first A / D converter 93 is converted from an analog value to a digital value.

This digital signal contains a digital signal from that of the electromotive force cell 24 generated terminal voltage Vs. The terminal voltage Vs, the oxygen concentration corresponding to the electromotive force cell 24 is generated by the digital filter unit 99 modified to become a low-frequency electrical signal which, compared to the voltage across both terminals of the pumping cell 14 is generated by the pumping current Ip, changed by a small amount per unit time.

The digital filter unit 99 performs a low-pass filter-like digital process for extracting a signal of low-frequency components equal to or lower than the predetermined cut-off frequency (150 Hz in this embodiment) from the digital signal provided by the digital signal receiving unit 98 was received.

In this way, the digital filter unit extracts 99 the electrical signal of the low-frequency components, which are equal to or lower than the cut-off frequency, from the electrical signal from the electromotive force cell 24 via the Vs + connection 41 and the first operational amplifier 33 to the A / D converter 93 is transmitted. The low-frequency components passing through the digital filter unit 99 are extracted into the pumping current control unit 100 entered.

An example of a digital low-pass filter for use in the present invention is shown in FIG US 2013/0054663 , the entire disclosure of which is incorporated herein by reference.

The pumping current control unit 100 performs a feedback control of the pumping current Ip, that of the pumping cell 14 based on the low-frequency components passing through the digital filter unit 99 through, thereby oxygen in and out of the diffusion chamber 20 to pump. In particular, the low-frequency components passing through the digital filter unit 99 are extracted as the terminal voltage Vs of the electromotive force cell 24 used and the pumping current Ip, that of the pumping cell 14 is subjected to PID control, so that the low-frequency components (terminal voltage Vs) approach the target voltage value, thereby oxygen in and out of the diffusion chamber 20 to pump.

The digital control unit 31 , with the CPU configured in this way 91 , according to, even if high-frequency noise components, such. As the pump current Ip, the electrical signal from the electromotive force cell 24 via the Vs + connection 41 and the first operational amplifier 33 to the digital control unit 31 is transmitted, the digital filter unit 99 of the processor 91 cancel out these high-frequency noise components. Thus, it can be prevented that the high-frequency noise components in the pumping current control unit 100 penetration. In other words, since the CPU 91 as a digital filter unit 99 works, the terminal voltage Vs of the electromotive force cell 24 , which has been generated according to the oxygen concentration, the pumping current control unit 100 while extinguishing the high-frequency noise components.

As a result, the digital control unit 31 the terminal voltage Vs of the electromotive force cell 24 In addition, it can detect the oxygen concentration within the diffusion chamber 20 Detect with high accuracy based on the pump current Ip. Because the digital control unit 31 the pumping current Ip corresponding to the actual oxygen concentration within the diffusion chamber 20 can suitably control, oscillations of the terminal voltage Vs can be suppressed.

1.5. effects

According to the engine control system 1 This embodiment includes, as described above, the gas sensor control device 2 the digital control unit 31 (especially the CPU 91 ) acting as the digital filter unit 99 works.

Thus, even if the high frequency noise components, such. As the pump current Ip, the electrical signal from the electromotive force cell 24 via the Vs + connection 41 and the first operational amplifier 33 to the digital control unit 31 are superimposed, these high-frequency noise components through digital processing, which through the digital filter unit 99 is executed, be extinguished. Thus, the terminal voltage Vs of the electromotive force cell 24 , which has been generated in accordance with the oxygen concentration, are suitably extracted.

Accordingly, in the digital control unit 31 (especially the CPU 91 ), the pumping current control unit 100 a suitable feedback control of the pump current Ip, based on the low-frequency components passing through the digital filter unit 99 extracted.

Because the digital control unit 31 the pumping current Ip based on the actual terminal voltage Vs present in the electromotive force cell 24 according to the oxygen concentration within the diffusion chamber 20 is generated, controls to an appropriate value, the terminal voltage Vs can be controlled so as to approach the target voltage value, and oscillations of the terminal voltage Vs can be suppressed.

That is, the gas sensor control device 2 may cause the terminal voltage Vs to approach the target voltage value by the pump current Ip based on the low-frequency components passing through the digital filter unit 99 extracted, controlled in a feedback manner. This is achieved without using a configuration according to which pumping current with high frequency components into the electromotive force cell 24 flows, wherein the pumping current is obtained by extinguishing the low-frequency components of a predetermined cutoff frequency or lower frequencies from the pumping current Ip.

1.6. Corresponding structure

The relationship between the terms used to define the invention and the corresponding structure of the first embodiment will be described below.

The gas sensor control device 2 corresponds to an example of the sensor control device, the porous diffusion layer 18 corresponds to an example of a diffusion rate-controlling layer, the exhaust gas corresponds to an example of a gas to be measured, the oxygen corresponds to an example of a specific gas component, the terminal voltage Vs corresponds to an example of one Detection voltage and the gas sensor 8th corresponds to an example of a sensor.

Furthermore, the digital control unit corresponds 31 an example of a control unit, the CPU 91 to perform the function of the digital filter unit 99 corresponds to an example of a low-pass filter unit and the first A / D converter 93 corresponds to an example of an A / D voltage converter unit.

Second embodiment

As a second embodiment, hereinafter will be a gas sensor control device 102 that has a low pass filter 111 in the form of an analog circuit has been described.

In the following description, those parts of the second embodiment having the same configurations as those of the first embodiment will be denoted by the same symbols, respectively, an explanation thereof will be omitted. The description is mainly directed to those parts of the second embodiment which are different from the first embodiment.

4 FIG. 13 is a diagram showing the overall configuration of a second engine control system. FIG 101 shows which the second gas sensor control device 102 includes. 5 is a functional block diagram of a flow control by the CPU 91 the digital control unit 31 is performed according to the second embodiment.

The second gas sensor control device 102 includes the digital control unit 31 to perform the various types of sequencing, the first operational amplifier 33 , a low pass filter 111 , the second operational amplifier 35 , the third operational amplifier 37 , the connections 39 for external connections, the constant current output unit 61 , the constant current source circuit 62 , the serial communication port 53 , Etc.

The hardware configuration of the second gas sensor control device 102 According to the second embodiment, the configuration of the gas sensor control device differs 2 the first embodiment in that the low-pass filter 111 is added. Further, the second gas sensor control device is different 102 from the configuration of the gas sensor control device 2 in that on the digital filter unit 99 the functional blocks of the CPU 91 is waived.

Next, the effects of the low-pass filter 111 (hereinafter also referred to as an LPF 111 ), while the output voltage Vs of the electromotive force cell 24 is controlled so that it approaches the target voltage.

As in 4 shown is the low pass filter 111 in a path from the Vs + port 41 towards the non-inverting input terminal of the first operational amplifier 33 provided. The input connection 112 the low-pass filter 111 is with the Vs + connection 41 connected, and the output terminal 113 the low-pass filter 111 is connected to the non-inverting input terminal of the first operational amplifier 33 connected.

6 shows the circuit diagram of the low-pass filter 111 ,

As in 6 shown is the low pass filter 111 by an analog circuit having a resistive element 114 and a capacitor 115 configured. The resistance element 114 is between the input terminal 112 and the output terminal 113 connected. The capacitor 115 is between the output terminal 113 and a ground wire connected.

The resistance of the resistive element 114 and the capacitance value of the capacitor 115 are selected so that the low-pass filter 111 pass a signal of low frequency components equal to or lower than a predetermined cutoff frequency (150 Hz in this embodiment).

The terminal voltage Vs, across both terminals of the electrometric force cell 24 is generated in accordance with the oxygen concentration is modified by the low-pass filter to produce a low-frequency electrical signal, which, compared to the voltage at both terminals of the pumping cell 14 is generated by the pumping current Ip by a small amount per unit time. The cutoff frequency of the low pass filter 111 is set in advance so that the low-frequency components of the terminal voltage Vs of the electromotive force cell 24 , which are generated according to the oxygen concentration, pass the low-pass filter.

Thus, the electric signal of the low-frequency components, which is equal to or lower than the cut-off frequency, through the low-pass filter 111 extracted from the electrical signal from the electromotive force cell 24 via the Vs + connection 41 to the non-inverting input terminal of the first operational amplifier 33 is transmitted, and is via the first operational amplifier 33 in the digital control unit 31 entered.

Even if high-frequency noise components, for example the pumping current Ip, are superimposed on the electrical signal, that of the electromotive force cell 24 via the Vs + connection 41 and the first operational amplifier 33 to the digital control unit 31 is transmitted, the low-pass filter 111 cancel out these high-frequency noise components. Consequently, the high-frequency noise components can be prevented from being introduced into the digital control unit 31 enter. That is, by providing the low pass filter 111 can the terminal voltage Vs of the electromotive force cell 24 , which is generated according to the oxygen concentration, in the digital control unit 31 while extinguishing the high-frequency noise components.

As a result, the digital control unit 31 the terminal voltage Vs of the electromotive force cell 24 detect with high accuracy, and can further detect the oxygen concentration based on the pump current Ip with high accuracy. Because the digital control unit 31 suitably the pumping current Ip corresponding to the actual oxygen concentration within the diffusion chamber 20 can control, oscillations of the terminal voltage Vs due to the influence of noise, etc. can be suppressed. Further, the terminal voltage Vs of the electromotive force cell 24 be brought to approach the target voltage.

2.2. effects

As described above, the second engine control system includes 101 According to the second embodiment, the second gas sensor control device 102 the low pass filter 111 , It follows that, even if high-frequency noise components of the electric signal, that of the electromotive force cell 24 via the Vs + connection 41 and the first operational amplifier 33 to the digital control unit 31 be superimposed, the low-pass filter can wipe out the high-frequency noise components. Accordingly, the terminal voltage Vs of the electromotive force cell 24 , which is generated according to the oxygen concentration, are suitably extracted.

Thus, the digital control unit 31 the pump current Ip, based on the low-frequency components passing through the low-pass filter 111 were extracted, fed back taxes.

Because the digital control unit 31 the pumping current Ip, based on the actual terminal voltage Vs, in the electromotive force cell corresponding to the oxygen concentration within the diffusion chamber 20 is generated, controls to an estimated value, the terminal voltage Vs can be made to reach the target voltage value, and oscillations of the terminal voltage Vs can be suppressed.

That is, the second gas sensor control device 102 may control the terminal voltage Vs to approach the target voltage value by the pump current Ip based on the low-frequency components passing through the low-pass filter 111 be extracted, controlled in a feedback manner. This can be achieved without using a configuration according to which a pumping current with high-frequency components obtained by canceling the low-frequency components of a predetermined cutoff frequency or lower frequencies from the pumping current Ip to the electromotive force cell 24 flows.

2.3. Corresponding structure

The relationship between the terms used to define the invention and a corresponding structure of the second embodiment will now be described.

The gas sensor control device 102 corresponds to an example of the sensor control device, the porous diffusion layer 18 corresponds to an example of a diffusion rate-controlling layer, the exhaust gas corresponds to an example of the gas to be measured, the oxygen corresponds to an example of the specific gas component, the terminal voltage Vs corresponds to an example of the detection voltage and the gas sensor 8th corresponds to an example of the sensor.

Furthermore, the digital control unit corresponds 31 an example of a control unit, the low-pass filter 111 corresponds to an example of a low-pass filter unit and the first A / D converter 93 corresponds to an example of a low-frequency A / D conversion unit.

3. Modifications

Although the above description has been made to specify embodiments of the invention, the invention is not limited to them and can be implemented in various ways without departing from the spirit of the invention.

For example, the cutoff frequency of the digital filter unit 99 and the low-pass filter 111 not limited to the above-mentioned value, and the digital filter unit 99 as well as the low-pass filter 111 can be configured to give you a goal and / or have an appropriate cut-off frequency.

Next, although the low-pass filter 111 has been configured according to the second embodiment by a single resistance element and a single capacitor element, instead of the low-pass filter 111 a second low pass filter 121 used, which is configured with two resistor elements and two capacitor elements.

7 is an explanatory diagram showing the configuration of the second low-pass filter 121 shows.

The second low pass filter 121 is configured by an analog circuit that is a resistive element 122 , a capacitor 123 , a resistance element 124 and a capacitor 125 includes.

A series connection of the resistance element 122 and the resistance element 124 is between the input terminal 112 and the output terminal 113 connected. The capacitor 123 is connected at one end to a connection point which is between the resistance element 122 and the resistance element 124 is arranged, and is connected to the other end with a ground conductor. The capacitor 125 is between the output terminal 113 and connected to the earth conductor.

The resistance values of the resistor element 122 and the resistance element 124 and the capacitance values of the capacitor 123 and the capacitor 125 are set to be the second low-pass filter 121 lets pass a signal of low frequency components of a predetermined cutoff frequency or lower frequencies.

The configured second low-pass filter 121 may instead of the low-pass filter 111 of the second embodiment.

Alternatively, as a third low-pass filter 131 a positive-feedback low-pass filter using an operational amplifier instead of the low-pass filter 111 be used.

8th is an explanatory diagram showing the configuration of the third low-pass filter 131 shows.

The third low pass filter 131 is configured by an analog circuit that is a resistive element 132 , a capacitor 133 , a resistance element 134 , a resistance element 135 , a capacitor 136 , a capacitor 137 and an operational amplifier 138 includes.

A series connection of the resistance element 132 , the resistance element 134 and the resistance element 135 is between the input terminal 112 and the non-inverting input terminal of the operational amplifier 138 connected. The capacitor 136 is connected at one end to a connection point which is between the resistance element 132 and the resistance element 134 is arranged, and is connected to the other end to the ground conductor. The capacitor 136 is between the non-inverting input terminal of the operational amplifier 138 and connected to the earth conductor. The capacitor 137 is at one end with the connection point between the resistance element 134 and the resistance element 135 is connected at the other end to the output terminal of the operational amplifier 138 connected. The output terminal of the operational amplifier 138 is connected to the inverting input terminal of the operational amplifier.

The resistance values of the respective resistance elements and the capacitance values of the respective capacitors are set so that the third low-pass filter 131 lets pass a signal of low frequency components of a predetermined cutoff frequency or lower frequencies.

The third low-pass filter configured in this way 131 may instead of the low-pass filter 111 of the second embodiment.

In the digital control unit 31 According to the second embodiment, a digital arithmetic circuit can be replaced by an appropriate hardware configuration of circuit elements instead of the CPU 91 be used. In this case, the strength of the pumping current Ip, the pump cell 14 be subjected to a PID control, so that the electromotive force (terminal voltage Vs) of the electromotive force cell 24 450 mV; and a subsequently calculated digital signal of the pumping current Ip may be applied to the D / A converter 94 be issued. Further, in the first and second embodiments, the digital control unit 31 with a serial communication port 53 provided, and the gas detection signal (Vip signal) by the CPU 91 is detected, is sent to the engine control unit 9 output. However, both the gas sensor control device and the second gas sensor control device may be configured to access the serial communication port 53 and the detection process of the gas detection signal (Vip signal) on the CPU 91 can be dispensed with, and a terminal voltage across both terminals of the current detection resistor 83 is sent to the engine control unit 9 output.

This invention has been described in detail with reference to the above embodiments. However, this invention should not be construed as limited to these embodiments. It should be apparent to those skilled in the art that various changes in the form and detail of the invention as described above may be made. It is intended that such changes be included in the spirit and scope of the appended claims.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 2624704 [0005]
• JP 5-256817A [0005]
• JP 2002-243700 A [0006]
• US 2013/0054663 [0082]

Claims (3)

A sensor control apparatus for controlling a sensor, the sensor including a diffusion chamber into which a gas to be measured flows through a diffusion rate controlling layer, an electromotive force cell generating a detection voltage corresponding to a concentration of a specific gas component within the diffusion chamber, and a pump cell; which pumps the particular gas component into or out of the diffusion chamber according to an externally provided pumping current, wherein the sensor control device comprises: a control unit configured to feedback control the pumping current based on the detection voltage so that the detection voltage generated at the electromotive force cell approaches a target voltage; and a low-pass filter unit configured to extract a predetermined low-frequency component from the detection voltage, wherein the control unit controls the pumping current fed back based on the low-frequency component extracted by the low-pass filter unit. A sensor control device according to claim 1, further comprising: an analog-to-digital voltage converter which converts the detection voltage generated at the electromotive force cell of the sensor from an analog value into a digital value, wherein the low-pass filter unit performs a digital operation on the digital value of the detection voltage converted by the analog-to-digital voltage converter to thereby extract the low-frequency component, and wherein the control unit controls the pumping current fed back through a digital process based on the digital value of the low-frequency component. A sensor control device according to claim 1, further comprising: a low-frequency analog-to-digital converter which converts the low-frequency component extracted by the low-pass filter unit from an analog value into a digital value, wherein the low-pass filter unit is an analog circuit provided in a detection path of the detection voltage from the electromotive force cell to the control unit, and wherein the control unit controls the pumping current fed back through a digital process based on the digital value of the low-frequency component converted by the low-frequency analog-to-digital converter.

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